The present invention relates to a method, a computer program product, and a device for projecting an exfoliated picture, and more specifically, to a method, a computer program product, and a device for projecting an exfoliated picture of tubular tissues.
Conventionally, medical image information relating to internal organs created by diagnostic medical imaging devices, such as diagnostic x-ray devices, computer tomography (CT) x-ray devices, magnetic resonance imaging devices (MRI devices), and the like, are used in performing medical procedures such as medical diagnostics and treatment. Medical image information is processed to obtain an image which can be displayed three-dimensionally, and the image is viewed three-dimensionally for the purpose of diagnosis or treatment. For example, there are three-dimensional display methods as described below for displaying images of tubular organs among organs such as blood vessels, the trachea, and digestive tract.
One such method is the parallel projective method which externally renders a tubular organ with parallel rays, and projects the tubular organ onto a two-dimensional plane. As shown in FIG. 1, a parallel projection image P1 created by the parallel projective method is suited for viewing a tubular organ from the outside. However, the user cannot view the interior of the tubular organ in the parallel projection image P1. The perspective projective method, for example, can be used for viewing the interior of a tubular organ. In the perspective projective method, an image of the interior of a tubular organ, rendered by light rays radially radiated from a viewpoint set within the tubular organ, is projected onto a two-dimensional plane. The perspective projective image P2 shown in FIG. 2, for example, can be created by the perspective projective method. The perspective projective image P2 can be used as a virtual endoscope so as to display an image of the interior side of tubular organs just as if viewed through an endoscope. A user can view the inside of the tubular organ using the perspective projective image P2. However, when a user does not closely examine the entirety of the interior circumference of the tubular organ, there is concern a polyp or the like may be overlooked. Furthermore, it is difficult to see the back side of folds present in tubular organs in the perspective projective image P2.
An article by Vilanova Bartroli et al., “Virtual Colon Unfolding,” appearing in the United States publication, IEEE Visualization (2001, p. 411-420), describes an exfoliated picture display in which a tubular organ is projected onto a cylindrical projection surface virtually disposed around a tubular organ by the cylindrical projection method or the curvature cylindrical projection method. The projection image is sliced from the side of the cylindrical surface so as to be unfolded on a two-dimensional surface. An exfoliated picture P3, such as that shown in FIG. 3, is created by the exfoliated picture display. In the exfoliated picture P3, polyps and the like can be readily discovered since the inner wall surface of the tubular organ can be viewed on a two-dimensional surface.
In the exfoliated picture P3, however, it is difficult to understand the observation position and observation direction. Tubular organs are sometimes twisted, or the direction in which the tubular organ extends sometimes changes. Accordingly, for example, the region which corresponds to the lower part of the tubular organ moves on the exfoliated picture P3 even when the image of the tubular organ is unfolded so as to position the bottom part at the proximal portion of the tubular organ in the center in the exfoliated picture P3. That is, in the exfoliated picture P3, the user can comprehend the relative position of the inner wall surface of the tubular organ, but cannot comprehend the absolute position (coordinates) of the inner wall position of the tubular organ. It is therefore difficult to recognize where in the tubular organ the observation position is located in the exfoliated picture P3. Further, it is difficult to avoid re-examining an already examined location in the exfoliated picture P3. It is also difficult to determine the observation direction in the exfoliated picture P3.
Among tubular organs, rinsing (internal residue) of the interior of the intestines may be present. Rinsing may accumulate in the lower side of intestines during a CT scan to create an exfoliated picture P3. Users often mistake rinsing represented in the exfoliated-picture P3 as polyps.